We report a visual motion aftereffect (MAE) that reveals simultaneous adaptation in independent motion channels coding for 'slow' or for 'fast' velocities. Dynamic random noise test patterns with low refresh frequencies or static test patterns can be used to test for MAEs mediated by slow channel adaptation, whereas MAEs produced by fast channel adaptation may be detected with noise patterns refreshed at high rates. After adaptation to transparent motion containing both a slow and a fast component, test patterns containing both high and low refresh frequencies produce a transparent, two-component MAE, revealing two distinct channels.